Abstract:

A shroud for supporting a variable vane in a compressor section for a gas
turbine engine includes a pair of components which are secured together
by a threaded fastener extending into a blind hole in one of the two
components. Additional material forms on the component which includes the
blind hole extends beyond a pivot axis for the vane such that there is an
increased length of engagement between the threaded fastener and the
blind hole. The blind hole eliminates the need for multiple nuts and
reduces the radial height of the shroud to save additional weight.

Claims:

1. A compressor section for use in a gas turbine comprising:a plurality of
rotors for rotation about an axial center line and at least one variable
vane assembly positioned axially intermediate said plurality of rotor
stages; andan inner shroud for mounting a radially inner portion of a
variable vane in said variable vane assembly, and an actuator mechanism
for causing said variable vane to pivot about a pivot axis, said inner
shroud including at least two components extending circumferentially, to
support a radially inner trunnion on said variable vane and said at least
two components being connected by a threaded fastener member extending
through a hole in a first of said at least two components and into a
blind hole in a second of said at least two components.

2. The compressor section as set forth in claim 1, wherein there are only
two of said components, and each of said two components extend
circumferentially for 360.degree. about said axis.

3. The compressor section as set forth in claim 1, wherein there is an
upstream component and a downstream component, and said second component
is said upstream component.

4. The compressor section as set forth in claim 1, wherein said components
both having a support surface for supporting said radially inner trunnion
with said second component having additional material extending beyond
the pivot axis, said additional material including said blind hole to
increase a threaded securement length of said threaded fastener within
said blind hole.

5. The compressor section as set forth in claim 4, wherein said additional
material extends from locations circumferentially spaced between the
support positions for mounting said inner trunnion, and into slots in
said first component.

6. The compressor section as set forth in claim 4, wherein a bearing is
mounted between said inner trunnion and said support surfaces.

7. The compressor section as set forth in claim 6, wherein an
anti-rotation surface is formed on one of said at least two components,
and said bearing having structure for engaging said anti-rotation
surface.

8. The compressor section as set forth in claim 7, wherein said bearing is
formed of two separate parts, and at least one of said parts having a
flat surface, said anti-rotation surface also being flat, and said flat
surfaces being aligned with each other to prevent rotation of said
bearing relative to said support surfaces.

9. The compressor as set forth in claim 4, wherein each of said components
having a radially outer support surface for supporting a radially outer
portion of said inner trunnion, and a radially inner support surface for
supporting a radially inner portion of said inner trunnion, and said
additional material extending circumferentially between said radially
inner support surfaces.

10. A shroud for supporting a variable vane in a compressor for a gas
turbine engine comprising:at least two components extending
circumferentially, to support a radially inner trunnion on a variable
vane and said at least two components being connected by a threaded
fastener member extending through a hole in a first of said at least two
components and into a blind hole in a second of said at least two
components.

11. The shroud as set forth in claim 10, wherein there are only two of
said components, and each of said two components extend circumferentially
for 360.degree. about a central axis.

12. The shroud as set forth in claim 10, wherein there is an upstream
component and a downstream component, and said second component is said
upstream component.

13. The shroud as set forth in claim 10, wherein said both components
having a support surface for supporting the inner trunnion, with said
second component having additional material for extending beyond a pivot
axis of the variable vane, said additional material including said blind
hole to increase a threaded securement length of said threaded fastener
within said blind hole.

14. The shroud as set forth in claim 13, wherein said additional material
extends from locations circumferentially spaced between the mount
positions for mounting the inner peg, and into slots in said first
component.

15. The shroud as set forth in claim 13, wherein a bearing is mounted
between the inner trunnion and support surfaces.

16. The shroud as set forth in claim 15, wherein an anti-rotation surface
is formed on one of said at least two components, and said bearing having
structure for engaging said anti-rotation surface.

17. The shroud as set forth in claim 16, wherein said bearing is formed of
two separate parts, and at least one of said parts having a flat surface,
said anti-rotation surface also being flat, and said flat surfaces being
aligned with each other to prevent rotation of said bearing relative to
support surfaces.

18. The shroud as set forth in claim 13, wherein each of said components
having a radially outer support surface for supporting a radially outer
portion of an inner peg, and a radially inner support surface for
supporting a radially inner portion of the inner peg, and said additional
material extending circumferentially between said radially inner support
surfaces.

Description:

BACKGROUND OF THE INVENTION

[0001]This application relates to a shroud for a variable vane structure
in a gas turbine engine, wherein the shroud is formed of two components
connected together by a threaded fastener extending into a blind hole in
one of the two components.

[0002]Gas turbine engines are known, and have a plurality of sections.
Typically, a compressor section receives air and compresses that air. The
air is delivered downstream to a combustor, and is mixed with fuel. The
air and fuel is combusted, and the products of combustion are passed
downstream over turbine rotors. The turbine rotors are driven to rotate.

[0003]The compressor section typically includes a plurality of rotor
stages and intermediate stationary vane stages. The rotor stages each
include a plurality of blades which have airfoils to receive and compress
air, and deliver that air downstream. Intermediate each stage of rotor
blades are stationary vanes. Under certain conditions it is desirable to
redirect the airflow between the compression stages. Thus, the vanes have
a variable profile, and may be caused to rotate on a pivot axis to
control the direction of air from one compression stage as it approaches
the next compression stage.

[0004]Such variable vanes are mounted in inner and outer shrouds. In the
prior art, at least some of these shrouds have been formed of at least
two separate components which meet along a flat mating surface at the
pivot axis of the vane. This prior art structure has included a hole
extending through both components. A threaded fastener, such as a bolt,
extends through the hole, and a nut is secured at an opposed end of the
hole. This structure requires a relatively great radial profile for the
shroud, due to the nut.

SUMMARY OF THE INVENTION

[0005]In a disclosed embodiment of this invention, the shroud for a
variable vane is formed of two components. A threaded fastener extends
through a hole in one of the components, and into a blind hole in the
other. The use of the blind hole provides a much smaller radial envelope
for the combined shroud and eliminates the need for multiple nuts to save
additional weight. In one feature of the disclosed embodiment, the
component which includes the blind hole has at least a portion extending
beyond the pivot axis for the vane such that there is a good deal of
additional material to receive the blind hole.

[0006]These and other features of the present invention can be best
understood from the following specification and drawings, the following
of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a view of a compressor section for a gas turbine engine.

[0008]FIG. 2 shows an exploded view of a variable vane and its inner
shroud structure.

[0009]FIG. 3 is a cross-sectional view through an assembly of the inner
shroud.

[0010]FIG. 4 is a cross-sectional view along a distinct portion of the
shroud of FIG. 2.

[0011]FIG. 5 is an assembled view of the shroud.

[0012]FIG. 6 is a radially inner view of the shroud shown in FIG. 5.

[0013]FIG. 7 shows an inner bearing feature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014]A compressor section 18 for a gas turbine engine is illustrated in
FIG. 1. The compressor section 18 has components which rotate about a
center axis 20. As known, rotors 22 are driven to rotate, and carry
blades 24. The blades have airfoils, and intermediate the stages of
rotors 22 are positioned stationary vanes 26. The vanes direct the
airflow from one compressor stage to the next.

[0015]As known, a shroud 30 secures an inner peripheral portion of the
vane 26, and supports it for pivotal movement. An outer trunnion 134 of
the vane 26 is driven to pivot by a linkage 33 connected to an actuator
34. As is known, the vane 26 is a variable vane, and can be caused to
pivot based upon operational conditions to control the direction of air
delivered from one compressor stage to the downstream compressor stage.
The times when such pivotal movement is desirable are within the level or
ordinary skill in the art. This application relates to the inner shroud
arrangement, and not to the movement of the vane 26 itself.

[0016]As shown in FIG. 2, the vane 26 has the radially outer trunnion 134,
and a radially inner platform 46, having a radially inner trunnion 35
which will be received within support structure in the inner shroud 30.
An upstream component 42 of the inner shroud 30 has a support surface 44
which is part-cylindrical, and conforms to the platform 46 of the vane
26. A downstream component 40 of the shroud 30 includes a similar part
cylindrical surface 146. Radially inner support surfaces 50 and 52
support the inner trunnion 35. A forwardly extending portion 54 will
extend beyond a pivot axis of the vane 26 as will be explained below. The
portions 54 fit into slots 51 which are circumferentially spaced between
support portions 50 on the component 40. A flat surface 48 serves to
allow component 42 material to extend beyond the pivot axis and prevent
rotation of a bearing (see FIG. 7). Although not shown, both components
40 and 42 extend for 360° about axis 20. In other embodiments,
multiple circumferential segments, such as 90°, may be used.

[0017]FIG. 3 is a cross-sectional view through the shroud 30 and shows the
relationship between components 40 and 42. As can be seen, the component
42 has portion 54 extending across the pivot axis X of the vane 26. As
further shown, the surfaces 50 and 52 support the lower trunnion 35. A
lower-most surface 37 is also supported between the components 40 and 42.

[0018]As shown in FIG. 4, this extending portion 54 provides additional
material to receive a threaded blind hole 60. A bolt 62 can be driven
into a recess 64 in the component 40 and into the blind hole 60 such that
a threaded element 66 can be secured into the blind hole 60 and secure
components 40 and 42 about the vanes 26. The additional material from
portion 54 provides a stronger component 42 and provides a greater
distance of threaded connection than would be available without the
additional material from portion 54. As can be seen, the threaded
distance includes the total of both distance F and distance G. The prior
art required a greater radial envelope R to provide its nut connection
than is required by this embodiment utilizing the blind hole 60.

[0019]FIG. 5 shows an assembled view. Platform 46 conforms to surfaces 44
and 146 for unrestricted flow. As can be seen in this figure, there are a
plurality of circumferentially spaced locations which will each receive a
vane 26, even though they are not all illustrated in this figure.

[0020]FIG. 6 shows a radially inner view of the shroud 30. The extending
portions 54 extend axially beyond the pivot axis X for the vanes 26, and
into slots 51. The vanes 26 are supported at locations circumferentially
spaced between the slots 51 and the extending portions 54.

[0021]FIG. 7 shows a split bearing assembly 70 and 72 which is mounted
about the trunnion 35, and which is the portion actually supported
between the surfaces 50 and 52, although not illustrated in the FIGS.
1-6. As can be seen, one of the bearing portions has a flat 74. Flat 74
sits against flat surface 48 preventing rotation of the bearing as the
vane 26 rotates about axis X.

[0022]Although a preferred embodiment of this invention has been
disclosed, a worker of ordinary skill in this art would recognize that
certain modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine the true
scope and content of this invention.